Horizontal articulated robot, and method of controlling the same

ABSTRACT

A robot includes a first horizontal arm coupled to a base, a second horizontal arm coupled to the base via the first horizontal arm, first and second motors adapted to rotate the respective arms, and first and second encoders adapted to calculate rotational angles and rotational velocities of the respective motors. A first motor control section subtracts first and second angular velocities based on the first and second encoders from a sensor angular velocity detected by an angular sensor, and controls the first motor so that a velocity measurement value obtained by adding a vibration velocity based on a vibration angular velocity as the subtraction result and a first rotational velocity becomes equal to a velocity command value.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation application of U.S. application Ser. No.13/400,922 filed Feb. 21, 2012, which claims priority to Japanese PatentApplication No. 2011-035860, filed Feb. 22, 2011, all of which areexpressly incorporated by reference herein in their entireties.

BACKGROUND

1. Technical Field

The present invention relates to a horizontal articulated robot equippedwith an angular velocity sensor, and a method of controlling thehorizontal articulated robot.

2. Related Art

In the past, there has been known a horizontal articulated robot whichperforms damping control of the arm using an angular velocity sensor fordetecting the angular velocity of the arm as described inJP-A-2005-242794 (Document 1). A first arm is coupled to a base of thehorizontal articulated robot described in Document 1 so as to be able torotate with respect to the base, and a second arm is coupled to the tipof the first arm so as to be able to rotate with respect to the firstarm. Further, when the first arm rotates due to the drive force of afirst drive source, the rotational angle of the first arm is detected bya first angle sensor for detecting the rotational angle of the firstdrive source, and the angular velocity of the first arm with respect tothe base is detected by a first angular velocity sensor mounted on thefirst arm. On this occasion, in the robot controller for controlling thedriving procedure of the first drive source, feedback control isperformed on the first drive source based on the data detected by thefirst angle sensor and the first angular velocity sensor so that thedata to be detected become equal to predetermined values.

Further, when the second arm rotates due to the drive force of a seconddrive source, the rotational angle of the second arm is detected by asecond angle sensor for detecting the rotational angle of the seconddrive source, and the angular velocity of the second arm with respect tothe base is detected by a second angular velocity sensor mounted on thesecond arm. On this occasion, in the robot controller described above,feedback control is performed on the second drive source based on thedata detected by the second angle sensor and the second angular velocitysensor so that the data to be detected become equal to predeterminedvalues similarly to the control procedure with respect to the firstdrive source. Thus, the damping control of the first and second arms isperformed.

Incidentally, in order to drive the angular velocity sensors describedabove, it becomes necessary to connect a variety of electric wires suchas wires for supplying the angular velocity sensors with electricity orwires for transmitting the detection signals of the angular velocitysensors between the angular velocity sensors and the controller. Suchelectric wires are also required for the drive sources besides theangular velocity sensors, and are generally connected to an externalcontroller through a hollow substrate. Therefore, in the case ofrespectively disposing the angular velocity sensors to the first andsecond arms as in the case of the horizontal articulated robot describedabove, the same number of electric wires as the number of angularvelocity sensors are required. As a result, the work of laying theelectric wires for the angular velocity sensors around becomescumbersome.

Incidentally, the vibration caused in the first arm is generallyamplified by another arm coupled to the first arm, and then reaches anend effector of the horizontal articulated robot. Therefore, it is truethat it is also possible to reluctantly omit the second angle sensor andthe second angular velocity sensor described above, and at the same timeperform only the damping control of the first drive source based on thedetection result of the first angular velocity sensor to therebysuppress the vibration of the end effector. However, the track drawn bythe first arm with respect to the base generally includes a largernumber of tracks with small curvature compared to the tracks drawn byother arms with respect to the base. Therefore, the chances of foldingthe electric wires drawn from the first arm increase, and further, thecurvature in the folded portions also becomes smaller compared to theelectric wires drawn from other arms. Therefore, since the electricwires connected to the first angular velocity sensor are required tohave higher durability than the electric wires connected to the secondangular velocity sensor, after all, it results that restrictions relatedto the layout of such electric wires and cumbersomeness of laying theelectric wires around still remain.

SUMMARY

An advantage of some aspects of the invention is to provide a horizontalarticulated robot and a method of controlling a horizontal articulatedrobot which makes it possible to reduce the number of angular velocitysensors used for damping control, and to lower the durability requiredto the electric wire connected to the angular velocity sensors.

An aspect of the invention is directed to a horizontal articulated robotincluding a first arm having a base end coupled to a base via at least ajoint, and rotating due to drive of a first motor, a first velocitymeasurement section adapted to measure a rotational velocity of thefirst motor, a control section adapted to perform feedback control onthe first motor so that a velocity measurement value based on themeasurement value of the first velocity measurement section becomesequal to a velocity command value, a second arm coupled to a tip of thefirst arm, and rotating due to drive of a second motor, a secondvelocity measurement section adapted to measure a rotational velocity ofthe second motor, an angular velocity calculation section adapted tocalculate an angular velocity of the first arm based on the rotationalvelocity of the first motor, and calculate an angular velocity of thesecond arm based on the rotational velocity of the second motor, and anangular velocity sensor disposed on the second arm, and adapted todetect an angular velocity, wherein the control section subtracts theangular velocity of the first arm and the angular velocity of the secondarm from the detection value of the angular velocity sensor to therebycalculate a vibration velocity as a rotational velocity of the firstmotor corresponding to a vibration angular velocity as a result of thesubtraction based on the vibration angular velocity, and then uses avalue obtained by adding the measurement value of the first velocitymeasurement section and the vibration velocity to each other as thevelocity measurement value.

According to the horizontal articulated robot of this aspect of theinvention, the angular velocity detected by the angular velocity sensoris an angular velocity including the angular velocities of therespective arms based on the rotational velocities of the correspondingmotors and the angular velocities of the respective arms based on thevibration. Therefore, it is possible to obtain the vibration angularvelocity as the angular velocity of the arm due to the vibration byobtaining the angular velocity of the arm based on the rotationalvelocity of the corresponding motor for each of the arms, and thensubtracting the angular velocity thus obtained from the angular velocitydetected by the angular velocity sensor. In the horizontal articulatedrobot having the configuration described above, the angular velocitiesof the first and second arms are calculated based on the measurementvalues of the first and second velocity measurement sections, and theseangular velocities are subtracted from the detection value of theangular velocity sensor to thereby calculate the vibration angularvelocity. Then, the first motor is controlled so that the velocitymeasurement value, which is a value obtained by adding the vibrationvelocity as the rotational velocity of the first motor corresponding tothe vibration angular velocity, and the measurement value of the firstvelocity measurement section to each other becomes equal to the velocitycommand value. In other words, since the first motor is controlled sothat the rotational velocity of the first motor taking the component ofthe vibration of the arm into consideration becomes equal to thevelocity command value, the vibration of the first arm can besuppressed. In other words, since it becomes unnecessary to dispose theangular velocity sensor on the first arm, it is possible to reduce thenumber of angular velocity sensors disposed, and at the same time,reduce the number of electric wires connected to the velocity sensors.As a result, the work of laying the electric wires related to theangular velocity sensors can be prevented from becoming cumbersome.Moreover, since the angular velocity sensor is disposed on the secondarm, it is possible to reduce the chances of folding the wires, and toincrease the curvature of the wires at the folded portions compared tothe electric wires connected to the angular velocity sensor disposed onthe first arm. As a result, the durability required for the electricwires connected to the angular velocity sensor can also be lowered.

The horizontal articulated robot of the above aspect of the inventionmay further include a first position detection section adapted to detecta rotational angle of the first motor, and the control section maycalculate the velocity command value based on a deviation between adetection value of the first position detection section and a positioncommand value.

According to the horizontal articulated robot described above, since thevelocity command value is the deviation between the detection value ofthe first position detection section and the position command value, itis possible to control the position of the first arm to be located atthe position indicated by the position command value while suppressingthe vibration of the first arm.

The horizontal articulated robot of the above aspect of the inventionmay further include a second position detection section adapted todetect a rotational angle of the second motor, the first velocitymeasurement section may calculate the rotational velocity of the firstmotor based on a detection value of the first position detectionsection, and the second velocity measurement section may calculate therotational velocity of the second motor based on a detection value ofthe second position detection section.

According to the horizontal articulated robot described above, the firstvelocity measurement section can calculate the rotational velocity ofthe first motor based on a detection value of the first positiondetection section. Further, the second velocity measurement section cancalculate the rotational velocity of the second motor based on adetection value of the second position detection section.

The horizontal articulated robot of the above aspect of the inventionmay be configured such that the first arm is an arm coupled to the basevia the joint.

According to the horizontal articulated robot described above, thedamping control of the arm coupled to the base can be performed.

Another aspect of the invention is directed to a method of controlling ahorizontal articulated robot including: measuring a rotational velocityof a first motor adapted to rotate a first arm having a base end coupledto a base via at least a joint, performing feedback control on the firstmotor so that a velocity measurement value based on the rotationalvelocity measured becomes equal to a velocity command value, measuring arotational velocity of a second motor adapted to rotate a second armcoupled to a tip of the first arm, calculating an angular velocity ofthe first arm based on the measured rotational velocity of the firstmotor, calculating an angular velocity of the second arm based on themeasured rotational velocity of the second motor, and obtaining adetection value of an angular velocity sensor disposed on the secondarm, wherein the angular velocity of the first arm and the angularvelocity of the second arm are subtracted from the detection value ofthe angular velocity sensor to thereby calculate a vibration velocity asa rotational velocity of the first motor corresponding to a vibrationangular velocity as a result of the subtraction based on the vibrationangular velocity, and then a value obtained by adding the rotationalvelocity of the first motor and the vibration velocity to each other isused as the velocity measurement value.

According to the method of controlling a horizontal articulated robot ofthis aspect of the invention, since the damping control of the first armcan be performed based on the detection value of the angular velocitysensor disposed on the second arm, it is possible to reduce the numberof angular velocity sensors disposed, and at the same time, reduce thenumber of electric wires connected to the angular velocity sensors. As aresult, the work of laying the electric wires related to the angularvelocity sensors can be prevented from becoming cumbersome. Moreover,since the angular velocity sensor is disposed on the second arm, it ispossible to reduce the chances of folding the wires, and to increase thecurvature of the wires at the folded portions compared to the electricwires connected to the angular velocity sensor disposed on the firstarm. As a result, the durability required for the electric wiresconnected to the angular velocity sensor can also be lowered.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein like numbers reference like elements.

FIG. 1 is a front view showing a front structure of a robot according toan embodiment of the invention.

FIG. 2 is an electric circuit block diagram showing an electricalconfiguration of the robot.

FIG. 3 is a functional block diagram showing a functional configurationof a first electric motor control section.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, a horizontal articulated robot according to an embodimentof the invention will be explained with reference to FIGS. 1 through 3.

As shown in FIG. 1, a base end portion of a first horizontal arm 12 as afirst arm rotating around a shaft center C1 along the vertical directionwith respect to a base 11 of the robot 10 is coupled to an upper endportion of the base 11. Inside the base 11, there are disposed a firstelectric motor 13 for rotating the first horizontal arm 12, and a firstreduction gear 14 coupled to a rotating shaft 13 a of the first electricmotor and having an output shaft 14 a fixedly coupled to the firsthorizontal arm 12. Further, when the drive force of the first electricmotor 13 is transmitted to the first horizontal arm 12 via the firstreduction gear 14, the first horizontal arm 12 rotates in a horizontalplane with respect to the base 11. Further, the first electric motor 13is provided with a first encoder 13E as a first position detectionsection for outputting a pulse signal corresponding to the amount ofrotation of the first electric motor 13.

To the tip portion of the first horizontal arm 12, there is coupled asecond horizontal arm 15 as a second arm rotating around the shaftcenter C2 along the vertical direction with respect to the firsthorizontal arm 12. Inside an arm main body 15 a constituting the secondhorizontal arm 15, there are disposed a second electric motor 16 forrotating the second horizontal arm 15, and a second reduction gear 17coupled to a rotating shaft 16 a of the second electric motor 16 andhaving an output shaft 17 a fixedly coupled to the first horizontal arm12. Further, when the drive force of the second electric motor 16 istransmitted to the second horizontal arm 15 via the second reductiongear 17, the second horizontal arm 15 rotates around the shaft center C2in a horizontal plane with respect to the first horizontal arm 12.Further, the second electric motor 16 is provided with a second encoder16E as a second position detection section for outputting a pulse signalcorresponding to the amount of rotation of the second electric motor 16.Above the arm main body 15 a, there is disposed an arm cover 18 forentirely covering the arm main body 15 a.

On the tip portion of the second horizontal arm 15, there is disposed aspline shaft 19 penetrating the arm main body 15 a and the arm cover 18and displaced with respect to the second horizontal arm 15. The splineshaft 19 is inserted so as to fit into a spline nut 19S disposed on thetip portion of the second horizontal arm 15, and is supported rotatablyand movably in the vertical direction with respect to the secondhorizontal arm 15.

Inside the second horizontal arm 15, there is installed a rotary motor20, and the drive force of the rotary motor 20 is transmitted to thespline nut 19S via a belt not shown. When the rotary motor 20 rotatesthe spline nut 19S positively and negatively, the spline shaft 19rotates positively and negatively around the shaft center C3 along thevertical direction. The rotary motor 20 is provided with a third encoder20E for outputting a pulse signal corresponding to the amount ofrotation of the rotary motor 20.

Inside the second horizontal arm 15, there is installed a lifting motor21 for rotating a ball screw nut 19B positively and negatively. When thelifting motor 21 rotates the ball screw nut 19B positively andnegatively, the spline shaft 19 rises and falls in the verticaldirection. The lifting motor 21 is provided with a fourth encoder 21Efor outputting a pulse signal corresponding to the amount of rotation ofthe lifting motor 21. A work section 25 coupled to a lower end of thespline shaft 19 is arranged to be able to be attached with, for example,a device for gripping a conveyed object, and a device for processing aprocessed object.

Further, inside the second horizontal arm 15, there is disposed anangular velocity sensor 30 for measuring the angular velocity of thesecond horizontal arm with respect to the base 11. As the angularvelocity sensor 30, there is adopted a vibratory gyroscope using aquartz crystal vibrator in the present embodiment. To the upper side ofthe second horizontal arm 15, there is coupled one end of a wiring duct33 having flexibility as a piping member having the other end coupled tothe base 11. The electric wires connected to the devices installedinside the second horizontal arm 15 such as the second electric motor16, the second encoder 16E, the rotary motor 20, and the lifting motor21 are laid around from the inside of the second horizontal arm 15 tothe inside of the base 11 through the wiring duct 33. Further, theelectric wires laid around from the inside of the second horizontal arm15 to the inside of the base 11 are bundled in the inside of the base 11to thereby be laid around to a control device 40, which is installed inthe outside of the base 11 to perform overall control of the robot 10with the electric wires connected to the first electric motor 13 and thefirst encoder 13E. The control device 40 calculates the angular velocityof the first horizontal arm 12 based on a variety of signals input fromthe angular velocity sensor 30 and so on, and controls the firstelectric motor 13 so that the vibration of the second horizontal arm 15is suppressed.

Hereinafter, an electrical configuration of the control device 40 willbe described with reference to FIG. 2.

As shown in FIG. 2, a position command generation section 41 of thecontrol device 40 calculates the target position of the work section 25based on the content of the process to be performed by the robot 10, andthen generates a track for moving the work section 25 to the targetposition. Further, the position command generation section 41 calculatesthe rotational angle of each of the motors 13, 16, 20, and 21 for eachpredetermined control period so that the work section 25 moves along thetrack, and then outputs the target rotational angles as a result of thecalculation to a motor control section 42 as a first position commandPc, a second position command Pc2, a third position command Pc3, and afourth position command Pc4, respectively.

The motor control section 42 is composed of a first electric motorcontrol section 43, a second electric motor control section 44, a rotarymotor control section 45, and a lifting motor control section 46.

Detection signals from the first encoder 13E, the second encoder 16E,and the angular velocity sensor 30 are input to the first electric motorcontrol section 43 besides the first position command Pc as a positioncommand value. The first electric motor control section 43 drives thefirst electric motor 13 by feedback control using the detection signalsso that the rotational angle calculated from the detection signal of thefirst encoder 13E becomes equal to the first position command Pc.

Besides the second position command Pc2, the detection signal from thesecond encoder 16E is input to the second electric motor control section44. The second electric motor control section 44 drives the secondelectric motor 16 by feedback control using these signals so that therotational angle calculated from the detection signal of the secondencoder 16E becomes equal to the second position command Pc2.

Besides the third position command Pc3, the detection signal from thethird encoder 20E is input to the rotary motor control section 45. Therotary motor control section 45 drives the rotary motor 20 by feedbackcontrol using these signals so that the rotational angle calculated fromthe detection signal of the third encoder 20E becomes equal to the thirdposition command Pc3.

Besides the fourth position command Pc4, the detection signal from thefourth encoder 21E is input to the lifting motor control section 46. Thelifting motor control section 46 drives the lifting motor 21 by feedbackcontrol using these signals so that the rotational angle calculated fromthe detection signal of the fourth encoder 21E becomes equal to thefourth position command Pc4.

Then, a configuration of the first electric motor control section 43will be explained with reference to FIG. 3.

As shown in FIG. 3, to a first subtractor 51 of the first electric motorcontrol section 43, there are input the first position command Pc fromthe position command generation section 41, and a position feedbackvalue Pfb from a rotational angle calculation section 52. In therotational angle calculation section 52, the number of pulses input fromthe first encoder 13E is counted, and at the same time, the rotationalangle of the first electric motor 13 corresponding to the first encoder13E is output to the first subtractor 51 as a position feedback valuePfb. The first subtractor 51 outputs the deviation between the firstposition command Pc and the position feedback value Pfb to a positioncontrol section 53.

The position control section 53 multiplies the deviation input from thefirst subtractor 51 by a position proportional gain Kp as apredetermined coefficient to thereby calculate a rotational velocity ofthe first electric motor 13 corresponding to the deviation. The positioncontrol section 53 outputs the signal representing a velocity commandvalue as the rotational velocity of the first electric motor 13 to asecond subtractor 54 as the velocity command Vc.

Besides the velocity command Vc described above, a velocity feedbackvalue Vfb as a velocity measurement value is input to the secondsubtractor 54 from a rotational velocity calculation section 55. Thesecond subtractor 54 outputs the deviation between the velocity commandVc and the velocity feedback value Vfb to a velocity control section 63.

The velocity control section 63 performs a predetermined calculationprocess using, for example, a velocity proportional gain Kv as apredetermined coefficient on the deviation input from the secondsubtractor 54 to thereby output a torque command Tc of the firstelectric motor 13 corresponding to the deviation to a torque controlsection 64. The torque control section 64 generates a currentcorresponding to the torque command Tc, and then supplies it to thefirst electric motor 13.

Then, the configuration of the rotational velocity calculation section55 will be explained in detail.

The rotational velocity calculation section 55 is composed of a firstrotational velocity calculation section 56, a first angular velocitycalculation section 57, an adder-subtractor 58, a second rotationalvelocity calculation section 59, a second angular velocity calculationsection 60, a vibration velocity calculation section 61, and an adder62.

In the first rotational velocity calculation section 56 as a firstvelocity measurement section, the pulse signal is input from the firstencoder 13E, and the first rotational velocity V1 fb as a rotationalvelocity of the first electric motor 13 is calculated based on thefrequency of the pulse signal. Further, the first rotational velocitycalculation section 56 outputs the first rotational velocity V1 fb tothe first angular velocity calculation section 57 and the adder 62.

In the first angular velocity calculation section 57 constituting theangular velocity calculation section, a reduction ratio N1 of the firstreduction gear 14 and the first rotational velocity V1 fb are multipliedby each other to thereby calculate a first angular velocity ωA1 m as theangular velocity of the first horizontal arm 12 based on the rotationalvelocity of the first electric motor 13. Then, the first angularvelocity calculation section 57 outputs the first angular velocity ωA1 mto the adder-subtractor 58.

In the second rotational velocity calculation section 59 as a secondvelocity measurement section constituting the angular velocitycalculation section, the pulse signal is input from the second encoder16E, and the second rotational velocity V2 fb of the second electricmotor 16 is calculated based on the frequency of the pulse signal.Further, the second rotational velocity calculation section 59 outputsthe second rotational velocity V2 fb to the second angular velocitycalculation section 60.

In the second angular velocity calculation section 60, a reduction ratioN2 of the second reduction gear 17 and the second rotational velocity V2fb are multiplied by each other to thereby calculate a second angularvelocity ωA2 m as the angular velocity of the second horizontal arm 15based on the rotational velocity of the second electric motor 16. Then,the second angular velocity calculation section 60 outputs the secondangular velocity ωA2 m to the adder-subtractor 58.

In addition to the first angular velocity ωA1 m and the second angularvelocity ωA2 m, a sensor angular velocity ωA2 as a detection signal ofthe angular velocity sensor 30 is input to the adder-subtractor 58.Here, in the robot 10 composed of the constituents described above, thesecond horizontal arm 15 on which the angular velocity sensor 30 isdisposed is rotating at an angular velocity obtained by combining thefollowing angular velocities of:

-   -   A. the first angular velocity ωA1 m corresponding to the        rotational velocity of the first electric motor 13;    -   B. the second angular velocity ωA2 m corresponding to the        rotational velocity of the second electric motor 16; and    -   C. a vibration angular velocity ωA1 s based on the vibration        reaching the second horizontal arm 15 via the first horizontal        arm 12.

Therefore, the sensor angular velocity ωA2 output by the angularvelocity sensor 30 includes the first angular velocity ωA1 m, the secondangular velocity ωA2 m, and the vibration angular velocity ωA1 s. In theadder-subtractor 58, the first angular velocity ωA1 m (A) and the secondangular velocity ωA2 m (B) described above are subtracted from thesensor angular velocity ωA2 described above. Then, the adder-subtractor58 outputs the vibration angular velocity ωA1 s as the subtractionresult to the vibration velocity calculation section 61.

In the vibration velocity calculation section 61, the vibration angularvelocity ωA1 s is multiplied by a predetermined proportional gain Kgp tothereby calculate the rotational velocity of the first electric motor 13for canceling out the vibration angular velocity ωA1 s as a vibrationvelocity V1 s. Then, the vibration velocity calculation section 61outputs the vibration velocity V1 s as the calculation result to theadder 62.

In the adder 62, the first rotational velocity V1 fb and the vibrationvelocity V1 s are added to each other. The adder 62 outputs a correctedrotational velocity V1 a as the addition result to the second subtractor54 as a velocity feedback value Vfb.

Then, the procedure of the control of the first electric motor 13 mainlyby the first electric motor control section 43 among the operations ofthe robot 10 described above will be explained. When the first positioncommand Pc is input to the first electric motor control section 43 fromthe position command generation section 41, the deviation between thefirst position command Pc and the position feedback value Pfb is outputto the position control section 53. Subsequently, the velocity commandVc corresponding to the deviation is output from the position controlsection 53, and the deviation between the velocity command Vc and thevelocity feedback value Vfb is output to the velocity control section63.

On this occasion, since the velocity feedback value Vfb is equal to theadditional value of the first rotational velocity V1 fb and thevibration velocity V1 s, the deviation input to the velocity controlsection 63 is arranged to have a value from which the component of thevibration velocity V1 s is eliminated, namely a value for canceling outthe vibration velocity V1 s. Further, the torque command Tccorresponding to the deviation described above is output from thevelocity control section 63, and subsequently, the current correspondingto the torque command Tc is supplied to the first electric motor 13 fromthe torque control section 64.

According to such a configuration, if, for example, the first horizontalarm 12 is rotating at an angular velocity higher than the velocitycommand Vc due to the vibration, the corrected rotational velocity V1 abecomes lower than the first rotational velocity V1 fb as much as anamount corresponding to the vibration velocity V1 s. Such a torquecommand Tc based on the velocity deviation is a torque command forreducing the rotational velocity of the first electric motor 13 as muchas an amount corresponding to the vibration described above while movingthe first horizontal arm 12 to the position indicated by the firstposition command Pc. Therefore, as a result that the first electricmotor 13 is driven by the torque command for canceling the vibration,damping of the first horizontal arm 12 is achieved.

Further, if, for example, the first horizontal arm 12 is rotating at anangular velocity lower than the velocity command Vc due to thevibration, the corrected rotational velocity V1 a becomes higher thanthe first rotational velocity V1 fb as much as an amount correspondingto the vibration velocity V1 s. Such a torque command Tc based on thevelocity deviation is a torque command for increasing the rotationalvelocity of the first electric motor 13 as much as an amountcorresponding to the vibration while moving the first horizontal arm 12to the position indicated by the first position command Pc. Therefore,as a result that the first electric motor 13 is also driven by thetorque command for canceling the vibration, damping of the firsthorizontal arm 12 is achieved.

As explained hereinabove, according to the robot 10 related to thepresent embodiment, the advantages recited as follows can be obtained.

1. According to the embodiment described above, the damping control ofthe first horizontal arm 12 can be performed based on the sensor angularvelocity ωA2 as the detection signal of the angular velocity sensor 30disposed on the second horizontal arm 15. In other words, since itbecomes unnecessary to dispose the angular velocity sensor 30 on thefirst horizontal arm 12, the number of electric wires connected to theangular velocity sensors can be reduced, and at the same time, the workof laying the electric wires around can be prevented from becomingcumbersome compared to the configuration of disposing the angularvelocity sensors respectively on the first and second arms.

2. Moreover, since the angular velocity sensor 30 is disposed on thesecond horizontal arm 15, it is possible to reduce the chances offolding the wires, and to increase the curvature of the wires at thefolded portions with respect to the electric wires connected to theangular velocity sensor 30 compared to the angular velocity sensordisposed on the first horizontal arm 12. As a result, the durabilityrequired for the electric wires connected to the angular velocity sensor30 can be lowered.

3. According to the embodiment described above, since the velocitycommand Vc is a value based on the deviation between the positionfeedback value Pfb from the rotational angle calculation section 52 andthe first position command Pc, it is possible to control the position ofthe first horizontal arm 12 to be located at the position indicated bythe first position command Pc while suppressing the vibration of thefirst horizontal arm 12.

It should be noted that the embodiment described above can be put intopractice with the following modifications if necessary.

-   -   In the embodiment described above, from the viewpoint of        obtaining the corrected rotational velocity V1 a of the first        electric motor 13, it is also possible to adopt the        configuration in which the first rotational velocity calculation        section 56 and the first angular velocity calculation section 57        are reluctantly omitted. In the adder-subtractor 58 in such a        configuration, it results that the difference between the sensor        angular velocity ωA2 from the angular velocity sensor 30 and the        second angular velocity ωA2 m of the rotation due to the second        electric motor 16 is output to the vibration velocity        calculation section 61 as a calculation result with respect to        the first horizontal arm 12. Further, it results that in the        vibration velocity calculation section 61, by performing        multiplication by the predetermined proportional gain Kgp, the        corrected rotational velocity V1 a is calculated. As a result,        it is possible not only to obtain the advantages listed as 1        through 3 above, but also to simplify the configuration of the        first electric motor control section 43.    -   The robot 10 according to the embodiment described above has the        first horizontal arm 12 coupled to the base 11, and the second        horizontal arm 15 coupled to the base 11 via the first        horizontal arm 12. Besides this configuration, it is possible        for the robot to have, for example, a third horizontal arm to be        coupled to the base via the first and second horizontal arms 12,        15. Further, it is also possible for the first horizontal arm 12        to be coupled to a third horizontal arm coupled to the base 11,        for example.    -   In the embodiment described above, the first rotational velocity        calculation section 56 detects the rotational velocity of the        first electric motor 13 based on the frequency of the pulse        signal input from the first encoder 13E. Besides this        configuration, from the viewpoint of calculating the rotational        velocity of the first electric motor 13, it is also possible,        for example, to separately dispose a velocity sensor to thereby        calculate the rotational velocity of the first electric motor 13        from the detection value of the velocity sensor. It should be        noted that the same can be applied to the second rotational        velocity calculation section 59.    -   In the robot 10 according to the embodiment described above, the        velocity command Vc corresponding to the deviation between the        first position command Pc from the position command generation        section 41 and the position feedback value Pfb calculated by the        rotational angle calculation section 52 is calculated in the        position control section 53. Besides this configuration, it is        also possible to adopt the configuration in which the position        command generation section 41 calculates the velocity command Vc        for each control period in advance in accordance with the target        position of the work section 25, and then outputs the velocity        command Vc to the second subtractor 54 to thereby reluctantly        omit the first subtractor 51, the rotational angle calculation        section 52, and the position control section 53.    -   The first electric motor control section 43 according to the        embodiment described above is provided with the first rotational        velocity calculation section 56 for obtaining the first        rotational velocity V1 fb of the first electric motor 13 based        on the signal input from the first encoder 13E, and then        outputting the first rotational velocity V1 fb to the first        angular velocity calculation section 57.

Besides this configuration, it is also possible to adopt theconfiguration in which the first rotational velocity V1 fb can be inputto the first angular velocity calculation section 57 from the outside ofthe first motor control section 43, or the configuration in which thefirst velocity calculation section 57 can obtain the first rotationalvelocity V1 fb using the signal from the first encoder 13E, to therebyreluctantly omit the first rotational velocity calculation section 56.It should be noted that the same can be applied to the second rotationalvelocity calculation section 59 and the second angular velocitycalculation section 60.

What is claimed is:
 1. A horizontal articulated robot comprising: abase; a first arm connected to the base; a first motor that rotates thefirst arm; a first velocity measurement section that measures a firstrotational velocity of the first motor; a second arm connected to thefirst arm; a second motor that rotates the second arm; a second velocitymeasurement section that measures a second rotational velocity of thesecond motor; an angular velocity calculation section that calculates afirst angular velocity of the first arm from the first rotationalvelocity, and calculates a second angular velocity of the second armfrom the second rotational velocity; an angular velocity sensor attachedto the second arm, the angular velocity sensor obtaining a detectionvalue corresponding to detected angular velocity; and a control sectionthat calculates a subtractive value by subtracting the first angularvelocity and the second angular velocity from the detection value of theangular velocity sensor, calculates a third rotational velocity of thefirst motor corresponding to the subtractive value, and controls thefirst motor by an additional value obtained by adding the firstrotational velocity and the third rotational velocity.
 2. The horizontalarticulated robot according to claim 1, further comprising: a firstposition detection section that detects a rotational angle of the firstmotor; wherein the control section calculates a velocity command valuefrom a deviation between a detection value of the first positiondetection section and a position command value.
 3. The horizontalarticulated robot according to claim 2, further comprising: a secondposition detection section that detects a rotational angle of the secondmotor, wherein the first velocity measurement section calculates thefirst rotational velocity from a detection value of the first positiondetection section, and the second velocity measurement sectioncalculates the second rotational velocity from a detection value of thesecond position detection section.
 4. The horizontal articulated robotaccording to claim 1, wherein the first arm is connected to the base viaa joint.
 5. A method of controlling a horizontal articulated robotcomprising: measuring a first rotational velocity of a first motor thatrotates a first arm connected to a base; measuring a second rotationalvelocity of a second motor that rotates a second arm connected to thefirst arm; calculating a first angular velocity of the first arm fromthe first rotational velocity; calculating a second angular velocity ofthe second arm from the second rotational velocity; obtaining adetection value of an angular velocity sensor attached to the secondarm; calculating a subtractive value by subtracting the first angularvelocity and the second angular velocity from the detection value of theangular velocity sensor; calculating a third rotational velocity of thefirst motor corresponding to the subtractive value; and controlling thefirst motor by an additional value obtained by adding the firstrotational velocity and the third rotational velocity.